We evaluated the postoperative pain relief and side-effects of continuous epidural infusion of three analgesic regimens following major thoracic and/or abdominal surgery. One hundred and twenty patients were randomly divided into three treatment groups: (1) 0.25% or 0.5% bupivacaine at a rate of 3–7 ml·hr−1, (2) 0.01% morphine at a rate of 1–2 ml·hr−1, (3) a combination of 0.125% or 0.25% bupivacaine and 0.0025% or 0.005% morphine at a rate of 2–4 ml·hr−1. The study continued for the first 48 postoperative hours. The effect of pain relief was evaluated by assessment of the further requirement for parenteral analgesics. Sixty-four percent of the patients given bupivacaine, 56% of the patients given morphine and 80% of the patients given the combination required no supplemental analgesics. Continuous epidural infusion of bupivacaine was associated with hypotension (21%) and with numbness and weakness of hands or legs (18%). Continuous epidural infusion of morphine was associated with pruritus (18%) and with peristaltic depression (12%). The combination regimen was associated with pruritus (17%) and with drowsiness (14%). We conclude that the combination of bupivacaine and morphine significantly provides superior analgesia with less deleterious complications compared with either bupivacaine or morphine alone.